A digital watermark, which is traditionally associated with a document, is embedded for preventing from being copied and forged, usually in a manner not alerting human viewers that such information is present. Such meta-information embedded in the digital watermark is particularly the case that stored and transmitted in relation to digital media and not easy to be decreased or vanished. Thus, such meta-information can be detected robustly and reliablely. Similarly, it is necessary to provide methods and systems for verifying the authenticity of paper media, such as documents and articles. The document or article should be inconspicuously embedded confidential structure characteristic of meta-information therein in order to provide reasonable security against forgery
Conventionally, as disclosed in Official Gazette of Japanese Patent Application Laid-Open No. 09-179494, confidential information to be recorded is binarized into blocks. The confidential information is denoted with data of distances (or pixels) between reference point marks and position discrimination marks.
However, in the above mentioned conventional technique, the image inputted by a scanner or other input apparatus must be accurately manipulated at the granularity of a single pixel during detecting process. If there is any spot on the paper or noise interference during printing or reading, that will give birth to a great influence on information detecting.
Moreover, in the above mentioned conventional technique, when scanning the print document into a computer by a scanner or other input apparatus, and detecting the confidential information, the inputting image will contain lots of interference noise components because of the spots on the print document introduced in printing and rotation distortion introduced in scanning, thereby causing the confidential information hardly to be read correctly.